1. Field of the Invention
The present invention relates to a system and method for providing program information from a server to a recording medium, and a recording medium used for the method.
2. Description of the Related Art
Recently, users may use communication terminals connected to communication networks such as the Internet to download and view digitized content information.
However, since content information can be easily copied, fraudulent actions tend to be taken violating copyrights. From the viewpoint of protecting content information from those fraudulent actions, the content information is generally recorded after being encrypted with an encryption key and it is decrypted at the time of reproduction. This type of content protection technology includes CPRM (Content Protection for Prerecorded Media), which employs standardized encryption key schemes, such as SD-Audio, SD-Video, SD-ePublish (SD electronic publishing) (see, for example, Non-Patent Document 1: 4C Entity, LLC, [online] (<URL:http://www.4Centity.com/> (Internet search, Feb. 13, 2006)). The encryption key scheme employed in this Non-Patent Document 1 is a single-key encryption scheme where a title key is encrypted once with a media-specific key. On the other hand, consideration is now being given to dual-key encryption schemes where a content key is encrypted twice with a user key and a media-specific key (see, for example, Patent Document 1: Japanese Patent Laid-Open No. 2007-13780). This type of dual-key encryption schemes is employed in, e.g., MQbic®.
That is, certain industries have concerned the use of recording media as SRM (Secure Removable Media) in different DRM (Digital Rights Management) techniques using the above-mentioned encryption schemes. In this case, such recording media include SD cards, etc.
However, when recording media are used as SRM in each of the DRM techniques, in some instances, only functions that are previously provided in such recording media may not suffice. Therefore, there is a need for recording media that enables functions (program information) to be added or updated that are required for each of the DRM techniques. Besides, such recording media requires an environment where the added functions are executed.
However, if the added/updated functions (program information) as mentioned above cannot be securely accepted by the recording media, the following problems occur: Some occasions may arise where the addition/update of functions may be performed on a recording medium that is held by an unauthorized user masquerading as the legitimate user (masquerading problem). Consequently, when such masquerade is practiced in the recording medium, the legitimate recording medium may be susceptible to attacks such as addition of malicious functions (program information) or data manipulation through, e.g., program function analysis performed by the unauthorized user. That is, such recording medium itself could create some security holes.